sis5513 fatal udma problems

[Jim Studt]

The sis5513 has for quite a while had fatal problems with udma on some
machines.  (At least the thelinuxstore PIAs with the P6SET-ML
motherboard, I have heard other people with the same problem).

The sis5513 driver deliberatly overrides the CONFIG_IDEDMA_AUTO and
the BIOS settings that might disable UDMA and forces UDMA which works
for a while then fails, attempts to fallback to a non-DMA mode and
fails that as well.

The logs end up with something along the lines of...
  hdc: timeout waiting for DMA
  ide_dmaproc: chipset supported ide_dma_timeout func only: 14
  hdc: irq timeout: status=0x58 { DriveReady SeekComplete DataRequest }
  hdc: status timeout: status=0xd8 { Busy }
  hdc: DMA disabled
  hdc: drive not ready for command
  ide1: reset: success
  hdc: status error: status=0x58 { DriveReady SeekComplete DataRequest }
  hdc: drive not ready for command
... but it nevers succeeds in the reset.  The drive never becomes ready.

I will make a patch, but I am uncertain what the `right' policy should
be.  I am inclined to first and foremost respect the CONFIG_IDEDMA_AUTO
flag, then to take the fastest mode which is both capable and enabled in
the bios.

Thoughts?  Please? :-)

-- 
                                     Jim Studt, President
                                     The Federated Software Group, Inc.